Electric fuse



Sept. 8, 1925. I 1,552,971

- F. c. UNGER ELECTRIC FUSE Filed Dec. 16, 1921 INVENTOR Frank C Urzger' BY W ATTORNEYS.

Patented Sept. 8, 1925.

FRANK C. UNGER, OF ST. LOUIS, MISSOURI.

ELECTRIC FUSE.

Application filed December 16, 1921. Serial No. 522,942.

board housing if the highest underwriters rating as to safety is desired.

The main object of my invention is to provide a device that enables a conventional cartridge fuse to be used with a dangerproof electric receptacle, namely, a receptacle of the kind whose contacts or live parts are concealed and protected by a permanent top plate or cover element in such a way as to eliminate the possibility of a person touching any live metal parts when the fuse is not in position or when the fuse is being installed or removed, such, for example, as the type of electric receptacle that is now used extensively in floors and walls for enabling an electrically-operated device to be connected to a supply circuit.

To this end I have deviseda device which consists of a hollow member of any preferred shape and construction, a pair of spaced; prongs, pins or other projections on said member that are adapted to be inserted through holes in the top plate or cover element of an electric receptacle of the general type previously referred to and engaged with the contacts of said receptacle, a conventional cartridge fuse inside of said member that establishes electrical connection between said prongs and which fuses in case the circuit in which said receptacle is arranged is subjected to an overload.

Figure 1 of the drawings is a vertical longitudinal sectional View of a device constructed in accordance with my invention; and

Figure 2 is a transverse sectional view, taken on the line 2-2 of Figure 1.

Referring to the drawings which illustrate the preferred form of my invention, A designates a hollow member of such construction that a conventional cartridge fuse can be arranged inside of same, so as to establish electrical connection between a pair of spaced metal prongs, pins or projections on the member A which are adapted to be inserted through holes in the top plate or cover element of an electric receptacle (not shown) whose contacts form part of an electric cir- (:uit. In the form of my invention herein illustrated the member A comprises a tubular-shaped part 1 of insulating material onto which a cap piece 2 of insulating material is screwed, spaced metal prongs C that project downwardly from said member, and a conventional cartridge fuse B arranged To all whom it may concern:

Be it known that I, FRANK C. UNGER, a citizen of the United States, residing at St. Louis, Missouri, have invented a certain new 5 and useful Improvement in Electric Fuses, of which the following is a full, clear, and exact description, such as will enable others skilled in the art to which it appertains to i make and use the same.

This invention relates to fuses of the kind that are used for protecting electric circuits.

One type of electric fuse that is now in general use and which is known commerciah 1y as a plug fuse, consists of an externally screw-threaded, hollow ,meinber equipped. with a fuse element and adapted to be screwed into an internally screw-threaded, open electric receptacle of the same general design as the incandescent lamp socket now in universal use.

Another type of electric fuse that is also used extensively and which is known as a cartridge fuse consists of a cylindrical shaped, hollow member equipped with a fuse element and provided at its ends with conducting portions that co-operate with other conducting portions forming part of an electric circuit. An objection common to both types of electric fuses above referred to is that they necessitate the use of an electric receptacle which is not safe or danger proof when not equipped with a fuse, as in the case of a plug fuse and also in the case of a cartridge fuse whose contacts are exposed at all times, even when the fuse is in operative position. For example, a socket of the type that is used with a plug fuse is unsafe when a fuse is not arranged in same, because it is possible for a person to accidentally insert his finger inside of the socket, and thus touch a live contact that forms part of the electric circuit in which the socket is arranged. The same is true of the receptacles used with cartridge fuses of the type that are intended to be removed or installed by means of a pair of insulated pliers or other insulated tool so as to prevent the workmans hands coming in contact with the live parts of the fuse holder. This is such a serious objection that fuse receptacles used on panel boards are required to be arranged in a separate compartment pro tected by an individual door separate and distinct from the main docr of the panel inside of the member A and provided with metal ferrules 5 that held pressed tightly against portions 5 3* on the prongs that are arranged inside of the member A. One of the prongs, the one at the left of Figure 1 is preferably permanently combined with the portion 1 of the member A and the other prong is removably mounted in a slot 8 in the end portion of the part 1. In assembling the parts of the device the cartridge B is slipped into the part 1 and the removable prong C is then inserted in the slot 8 in said part, and thereafter the cap piece 2' is screwed onto the externallyscrew-tlneaded portion 3 of the part l thus causing the angularly-disposed portions t of the prongs C to be clamped tightly aeainst the ferrules 5 of the cartridge fuse. I desired, the part 1 of the member J; may be provided with a sight opening covered by a piece of mica or other suitable transparent material 7 so as to enable a user to readily determine the condition of the cartridge fuse inside of the hollow insulated member of the fuse.

A device of the construction above described is a decided improvement on the electric fuses now in general use, in that it enables a conventional. cartridge fuse to be used with a dangenproof electric receptacle namely, a receptacle whose contacts are pro tected and covered by a permanent top plate or cover element which eliminates the possibility of a person accidentally touching or coming in contact with any live metal parts of the receptacle the fuse itself being protected by an insulating member which completely encases the fuse. h'loreover such a device can be n'ianu'lactnred and sold at a sufficiently low cost to enable it to compete with the electric fuses now in general use.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

A. device of the character described, consistinp; of a tubular member of insulating material closed at one end, a removable cap on said member that forms a closure for the other end of same, a conventional cartridge fuse removably mounted in said member, a stationary prong projecting; outwardly from said member and provided with an angularly-disposed portion arranged inside of said member that engages the metal ferrule on one end of said fuse, and a removable prong arranged in a slot in the end portion of said member closed by said cap and provided with an angularly-disoosed part that engages the metal ferrule on the other end of said fuse.

FRANK UNGER. 

